JP2015125280A - Grid polarizing element, method and apparatus for emitting polarized ultraviolet light, method for manufacturing substrate having optical alignment layer and optical alignment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-reflection type grid polarizing element easily manufactured and capable of stably obtaining a desired polarization performance even when used on the condition of easily causing oxidization using ultraviolet light as a target wavelength.SOLUTION: A striped grid 2 provided on a transparent substrate 1 has a main layer formed by titanium nitride and/or titanium oxynitride, is formed by a lot of linear parts 21 without including a single metal layer and polarizes light by selectively absorbing s polarized light and transmitting p polarized light. Each linear part 21 is spaced at an interval t allowing the polarization of ultraviolet light. The ultraviolet light from a mercury lamp 51 is polarized by a grid polarizing element 53, and a work piece 10 is optically aligned by irradiating the work piece 10 with the polarized ultraviolet light.

Description

  The invention of the present application relates to a grid polarizing element which is a kind of polarizing element.

  Various polarizing elements for obtaining polarized light are known as optical elements such as polarizing filters and polarizing films, as well as familiar products such as polarizing sunglasses, and are also widely used in display devices such as liquid crystal displays. Polarizing elements are classified into several types according to the method of extracting polarized light, and one of them is a wire grid polarizing element.

  The wire grid polarizing element has a structure in which a fine striped grid made of metal (conductor) is provided on a transparent substrate. By functioning as a polarizer by setting the spacing between a large number of linear portions constituting the grid to be equal to or less than the wavelength of light to be polarized. Of linearly polarized light, polarized light having an electric field component in the length direction of the grid is reflected because it is equivalent to a flat metal, whereas for polarized light having an electric field component in a direction perpendicular to the length direction, only a transparent substrate is reflected. Since it is equivalent to being, it is transmitted through the transparent substrate and emitted. For this reason, linearly polarized light in a direction perpendicular to the length direction of the grid is exclusively emitted from the polarizer. By controlling the orientation of the polarizing element so that the length direction of the grid is oriented in a desired direction, polarized light whose axis of polarized light (direction of the electric field component) is oriented in the desired direction can be obtained. .

  Hereinafter, for convenience of description, linearly polarized light having an electric field component in the length direction of the grid is referred to as s-polarized light, and linearly polarized light having an electric field component in a direction perpendicular to the length direction is referred to as p-polarized light. Usually, an object with an electric field perpendicular to an incident surface (a surface perpendicular to a reflecting surface and including incident light and reflected light) is called an s wave, and a parallel one is called a p wave. The distinction is made on the assumption that they are parallel.

  The basic indicators for the performance of such a polarizing element are the extinction ratio ER and the transmittance TR. The extinction ratio ER is the ratio of the intensity (Ip) of p-polarized light to the intensity (Is) of s-polarized light out of the intensity of polarized light transmitted through the polarizing element (ER = Ip / Is). Further, the transmittance TR is a ratio of the energy of outgoing p-polarized light to the total energy of incident s-polarized light and p-polarized light (TR = Ip / (Is + Ip)). An ideal polarizing element has an extinction ratio ER = ∞ and a transmittance TR = 50%.

Japanese Patent No. 5184624 Japanese Patent No. 5224252 Japanese Patent No. 5277455

  As the name suggests, the wire grid polarization element employs metal as the grid material, and obtains a polarization action by selectively reflecting the s wave to the grid as described above. According to the inventor's research, it has been found that the wire grid polarizing element exists as an inevitable problem of metal degradation.

  The manufacture of the wire grid polarization element is performed by forming a metal film on a transparent substrate and obtaining a fine grid structure by photolithography. In this case, there is often a heating step in the production, and the metal surface may be thermally oxidized. For example, aluminum is often used for the grid, but when a polarizing element obtained by forming an aluminum grid is exposed to air at a high temperature, it rapidly oxidizes and an alumina layer is formed on the surface.

  As described above, in the wire grid polarizing element, the distance (gap width) between the linear portions forming the grid is optimally designed in relation to the wavelength of light to be polarized. This design naturally takes into account the physical properties of the grid material, in particular the optical constants (n and k of the complex refractive index) as important parameters. Even when designed as an aluminum grid, if an oxide layer is formed on the surface, the optical constant may be different from that at the time of design, so that the desired polarization performance may not be obtained. Other metals, such as copper, may be used as the grid material, but the situation is similar. Although it is conceivable to use a metal that does not oxidize such as gold, fine processing may be difficult and cost problems may occur.

  Such deterioration of the grid can be caused not only by the factor at the time of manufacture but also by the factor at the time of use, that is, the use environment. Deterioration can easily occur when used in an easily oxidizable environment such as high temperature and humidity. Another example of deterioration due to the use environment is when the polarized light is ultraviolet light.

  As is well known, oxygen active species (for example, atomic oxygen) are generated by irradiation with ultraviolet rays, and the oxygen active species has a high oxidizing action. In particular, the oxidizing action of oxygen active species and ozone generated by ultraviolet rays of 300 nm or less is strong, and metals such as aluminum are rapidly oxidized. Also, in an optical process such as photo-alignment, it may be necessary to irradiate polarized light with higher illuminance in order to increase productivity. In this case, the metal may be heated and thermally oxidized by light irradiation with high illuminance.

For example, in the case of an aluminum grid, a thin film for the grid is usually formed by sputtering using an aluminum target, and a striped grid shape is formed by etching. Sputtering is performed by DC or high frequency, the input power density on the target sputtering surface is about 1 to 10 W / cm ² , the atmospheric pressure is about 0.01 to 0.1 Pa, and the flow rate of argon as the sputtering gas is 10 to 50 SCCM. The substrate temperature is about 20 to 100 ° C. When the aluminum film thus formed is irradiated with ultraviolet rays (380 nm or less), it is confirmed that aluminum is oxidized and the reflectance is lowered.

  Such a problem of metal oxidation due to light irradiation is also highlighted as a problem affecting the polarization mechanism itself of a conventional wire grid polarizing element. That is, the wire grid polarization element causes a polarization action by selectively reflecting the s-wave on the grid as described above. However, metals such as aluminum and copper easily absorb ultraviolet rays due to oxidation, resulting in a decrease in reflectance. For this reason, when a wire grid polarizing element composed of a grid formed of these metals is used for ultraviolet rays, the grid is oxidized in a short period of time, resulting in an increase in absorption, and a desired polarization performance (extinction ratio and transmittance) can be obtained. It will not be possible. Some metals have a high absorption rate of ultraviolet rays from the beginning, and some materials cannot be used for ultraviolet rays. Such a point has been found by the inventors' research.

  Patent Documents 1 to 3 that disclose a wire grid polarizing element adopt aluminum, silver, gold, or copper as the material of the element 26 (that is, the wire grid) that is a main layer that performs a polarizing action (for example, Patent Documents). 1, paragraph 0019) also refers to the polarization of ultraviolet light (for example, paragraph 0015 in Patent Document 1). However, in reality, the grid is oxidized due to ultraviolet irradiation and the reflectivity of the ultraviolet light is reduced, or from the beginning, the ultraviolet ray is absorbed and has little reflection. In other words, although Patent Documents 1 to 3 refer to the polarization of ultraviolet rays, they do not actually function as a reflective polarizing element, or provide only insufficient polarization performance.

  The inventor of the present application intends to construct a polarizing element based on a technical idea that is fundamentally different from the conventional wire grid polarizing element that is such a reflective type, and a polarizing element that can also be referred to as a non-reflective type, that is, an absorbing type. Completed. The polarizing element of the present invention is not a reflection type, and the main part that performs the polarizing action is not made of a single metal, and is hereinafter referred to as a grid polarizing element. The single metal is a metal (non-complex metal) that is not bonded to atoms other than other metals.

  Absorptive grid polarizing elements utilize the light absorption of the metal compounds and dielectrics as described above, and cause the polarizing action mainly due to the absorbing action. As will be described later, if a light-absorbing material is selected as the grid material, and the height of the grid is increased to some extent to increase the aspect ratio, the p-wave can be transmitted while the s-wave is selectively absorbed and attenuated. And a sufficient polarization effect can be obtained.

  In Patent Documents 1 to 3, absorption layers 34a and 34b are provided on the element 26 made of a single metal such as aluminum. According to the description in Patent Documents 1 to 3, the absorption layers 34a and 34b are for absorbing s-waves selectively reflected by the element 26 (wire grid) (for example, paragraphs in Patent Document 1). 0021). Probably, it is considered to be for the purpose of absorbing the reflected s-wave so that the s-wave reflected by the element 26 does not adversely affect the surroundings.

  The invention of this application has been made in consideration of the above-mentioned points, and is a non-reflective (absorptive) grid polarizing element that is easy to manufacture and has an oxidation wavelength that uses ultraviolet light as a target wavelength. It is an object of the present invention to provide an excellent grid polarizing element that can stably obtain desired polarization performance even when used under conditions that cause the occurrence of light.

In order to solve the above-mentioned problem, the invention according to claim 1 of the present application includes a transparent substrate and a striped grid provided on the transparent substrate, and selectively transmits specific polarized light out of incident light. Grid polarizing element that polarizes light by causing
A large number of linear portions forming the grid have a main layer formed of titanium nitride or titanium oxynitride, and are configured as non-reflective grid polarizing elements that do not include a single metal layer.
In order to solve the above-mentioned problem, the invention according to claim 2 is characterized in that, in the configuration of claim 1, when the width of each linear part forming the grid is w and the height is h, h / w is It has a configuration of 3 or more.
In order to solve the above-mentioned problem, the invention according to claim 3 is the configuration according to claim 1 or 2, wherein the linear portion is formed in a process in which light propagates in the thickness direction of the linear portion. Compared with the polarized light whose polarization axis is oriented in the direction perpendicular to the length direction of the linear portions, the polarized light whose polarization axis is oriented in the length direction of each linear portion is absorbed so that the light is polarized. It has the structure of being a thing.
In order to solve the above problem, the invention according to claim 4 is the configuration according to claim 1, 2, or 3, wherein the spacing between the linear portions forming the grid can polarize ultraviolet rays. It has a configuration of being an interval.
In order to solve the above-mentioned problem, the invention according to claim 5 has a structure in which, in the structure of claim 4, the spacing between the linear portions forming the grid is 100 nm or more and 200 nm or less.
In order to solve the above-mentioned problem, the invention described in claim 6 is arranged such that the non-reflective grid polarizing element according to claim 4 or 5 is disposed at a position where light from a mercury lamp including an emission line spectrum of 260 nm or less reaches. And, it has a configuration that is an ultraviolet polarized light irradiation method of irradiating an object with polarized light transmitted through the non-reflective grid polarizing element.
In order to solve the above problem, the invention according to claim 7 is a mercury lamp that emits light having an emission line spectrum of 260 nm or less;
It has the structure that it is an ultraviolet polarized light irradiation apparatus provided with the non-reflective grid polarizing element of Claim 4 or 5 arrange | positioned in the position where the light from this mercury lamp reaches | attains.
In order to solve the above problems, the invention according to claim 8 is the non-reflective grid polarizing element according to claim 4 or 5 arranged at a position where light reaches from a light source that emits ultraviolet rays. And a method of manufacturing a substrate with a photo-alignment layer, including a step of irradiating a film for photo-alignment layer with ultraviolet polarized light that has passed through a type grid polarizing element.
Moreover, in order to solve the said subject, invention of Claim 9 is an ultraviolet light source,
The non-reflective grid polarizing element according to claim 4 or 5 disposed at a position where light from an ultraviolet light source reaches,
The optical alignment apparatus includes a means for transporting or arranging a film for the photo-alignment layer at a position where the polarized light transmitted through the non-reflective grid polarization element is irradiated.

As described below, according to the grid polarizing element of claim 1 of the present application, the main layer of each linear portion is formed of titanium nitride and titanium oxynitride and does not include a single metal layer. Even if a grid polarizing element that operates in a model is obtained and used in an environment that easily oxidizes, deterioration of polarization characteristics does not become a problem. For this reason, it becomes a grid polarization element especially suitable when polarizing with ultraviolet rays as a target wavelength.
According to the second aspect of the present invention, in addition to the above effects, the aspect ratio of each linear portion is 3 or more, so the extinction ratio is higher in the absorption model, and high-quality polarized light can be obtained. .
According to the third aspect of the invention, in addition to the above-described effect, it operates with an absorption model, so that it is a grid polarizing element suitable for polarizing ultraviolet light.
According to the invention of claim 4 or 5, in addition to the above effects, ultraviolet polarized light can be obtained.
Further, according to the invention described in claim 6 or 7, in addition to the above effect, a polarizing action having a high extinction ratio can be obtained in the ultraviolet region of 260 nm or less, and therefore, it is possible to irradiate polarized light having a strong emission line with good quality. it can.
Further, according to the invention described in claim 8 or 9, since the polarization characteristics do not change due to the deterioration of the polarizing element even if the photo-alignment is performed while irradiating the high-illuminance ultraviolet polarized light, the desired photo-alignment treatment can be performed. The effect can be obtained stably and with high productivity.

1 is a schematic perspective view of a grid polarizing element according to a first embodiment of the present invention. It is the isometric view schematic shown about the operation | movement model of an absorption-type grid polarizing element. It is the front schematic which showed about the operation | movement model of the absorption-type grid polarizing element. It is the front sectional schematic diagram shown about the suitable manufacturing method of the grid polarizing element of a first embodiment. It is the figure which showed the result of the simulation which investigated the polarization performance about the Example of a grid polarizing element. It is a front sectional schematic diagram of a grid polarization element of a second embodiment. It is the front cross-sectional schematic shown about the manufacturing method of the grid polarizing element of 2nd embodiment shown in FIG. It is a front sectional schematic diagram of other embodiments of a grid polarization element. It is the figure which showed the outline of the manufacturing method of the board | substrate with a photo-alignment layer of embodiment, and is a cross-sectional schematic diagram of a photo-alignment apparatus.

Next, modes (embodiments) for carrying out the present invention will be described.
First, a first embodiment of the invention of the grid polarizing element will be described. FIG. 1 is a schematic perspective view of a grid polarizing element according to the first embodiment of the present invention. The grid polarization element shown in FIG. 1 includes a transparent substrate 1 and a grid 2 provided on the transparent substrate 1.

  The transparent substrate 1 is “transparent” in the sense that it has sufficient transparency with respect to the target wavelength (the wavelength of light polarized using a polarizing element). In this embodiment, since ultraviolet light is assumed as the target wavelength, quartz glass (for example, synthetic quartz) is employed as the material of the transparent substrate 1.

  As shown in FIG. 1, the grid 2 has a stripe (line and space) shape composed of a large number of linear portions 21 extending in parallel. Each linear portion 21 is linear in a plan view, but has a certain height h as shown in FIG. Moreover, each linear part 21 which forms the grid 2 has a width w, and each linear part 21 is separated by an interval (gap width) t. The grid 2 performs a polarizing action by such a three-dimensional structure of each linear portion 21 and a gap therebetween.

  In such a grid 2, titanium nitride is selected as the material of each linear portion 21 in this embodiment. Titanium nitride was selected as a material for each linear portion 21 in consideration of constituting the above-described absorption-type grid polarizing element and stably obtaining desired polarization characteristics regardless of use conditions. Is.

  According to the inventor's research, in order to construct an absorption-type grid polarizing element, it is necessary that the material of each linear portion 21 has an appropriate extinction coefficient (imaginary part of complex refractive index) k. However, the extinction coefficient k of titanium nitride is, for example, about 0.8 to 1.6 in the ultraviolet region of about 200 to 380 nm, which is a good material for the absorption grid 2.

  Further, as is well known, titanium nitride is a chemically stable material and is not easily deteriorated even when placed in an active atmosphere. The inventor paid particular attention to the fact that there is little change in the optical properties that affect the polarization characteristics even if some oxidation occurs due to exposure to oxidizing chemical species such as ozone and oxygen active species. is there.

The polarization characteristics of the grid polarizing element are defined by the optical properties of each linear part forming the grid, in particular the optical constants (complex refractive indexes n, k), in addition to the size and shape of the grid. In particular, in the absorption model described later, the imaginary part (extinction coefficient k) of the complex refractive index is important, and it is necessary to have an appropriate extinction coefficient k at the target wavelength.
Here, according to the inventor's research, the difference in the values of n and k of titanium nitride with respect to titanium oxynitride is small, particularly in the ultraviolet region of 380 nm or less. Furthermore, titanium nitride has a small difference in n and k values with respect to titanium oxide. Here, “small” means that the difference in optical constant between a single metal and an oxide of the single metal is small as in the case where aluminum is oxidized to alumina.

  When titanium nitride is exposed to oxidizing chemical species such as ozone and oxygen active species, it is speculated that a portion of the titanium nitride may be oxidized and converted to titanium oxynitride. Even in this case, the optical constant of titanium oxynitride is not significantly different from the optical constant of titanium nitride, so that the polarization performance is not greatly impaired. That is, a favorable polarizing action can be stably obtained under the dimensions designed as a titanium nitride grid (t, w and h shown in FIG. 1). In addition, although it seems that it is not usually possible, even if it is assumed that titanium nitride has changed to titanium oxide, there is no significant change in the optical constant, so under the dimensions designed as a titanium nitride grid Good polarization action can be obtained stably.

  Further, the selection of titanium nitride as the material of the grid 2 also has the significance that the manufacture of the polarizing element becomes easier. As is well known, titanium nitride is widely used as a barrier film (for example, a copper diffusion prevention film) and an electrode film (for example, a capacitor electrode film) in semiconductor integrated circuit elements (various memories and logic elements). For this reason, a technique for forming a fine structure using titanium nitride (film forming technique, etching technique, etc.) has been actively studied and established as a practical technique. When manufacturing the grid polarizing element of the embodiment, it is possible to apply a fine structure forming technique using titanium nitride established in such a semiconductor process.

  In particular, in the case of a grid polarization element, the gap width (t in FIG. 1) in the grid 2 needs to be equal to or less than the wavelength of light to be polarized. Therefore, when the ultraviolet light is polarized, the gap width must be narrower. In addition, finer processing is required as compared with a polarizing element for visible light. When a new material is selected as the material of the grid 2, it is necessary to develop a technique for forming the grid 2 having the necessary fineness with such a material from scratch. On the other hand, in the case of titanium nitride, since the fine processing technology established in the semiconductor process as described above can be applied, the selection of manufacturing conditions can be easily performed, and the manufacturing itself is also easy.

  Moreover, when compared with the wire grid polarizing element disclosed in Patent Documents 1 to 3, the grid polarizing element of the embodiment has an advantage that it is easier to manufacture from another viewpoint. The wire grid polarizing elements of Patent Documents 1 to 3 have a structure in which a dielectric multilayer film is provided on an element 26 made of a single metal. Single metals such as aluminum and copper are generally difficult to process and are difficult to etch.

  In Patent Documents 1 to 3, since the element 26 is a grid, it is necessary to have a fine structure and to form a striped pattern by etching. In this case, the upper dielectric multilayer film is etched to form stripes, and then the single metal layer is further etched to form the element 26. In the etching of the single metal, a highly reactive etchant is used. There is a need to. At this time, there is a possibility that the resist is consumed and the upper dielectric multilayer film may be scraped off, and it is not easy to select appropriate etching conditions. Further, when the element 26 is formed by etching the single metal layer, there is a problem that the metal material released by the etching adheres as a residue to the side surface of the dielectric multilayer film, which is greatly different from the optical structure in design. It can happen.

On the other hand, in the grid polarizing element of the embodiment, the grid 2 made of titanium nitride may be provided on the transparent substrate 1, so that there is no difficulty in obtaining a grid structure in which different materials are laminated. Etching of titanium nitride can be realized by a dry process (reactive ion etching) using, for example, carbon tetrafluoride (CF ₄ ) as an etchant, and there is no difficulty in selecting etching conditions.

  Next, an absorption-type polarization action model realized in such a titanium nitride grid 2 will be supplementarily described. 2 and 3 are schematic views showing an operation model of the absorption type grid polarizing element, FIG. 2 is a schematic perspective view, and FIG. 3 is a schematic front view. 2 and 3, for the sake of convenience, it is assumed that light propagates from the top to the bottom on the paper surface, and this direction is the z direction. Further, the direction in which each linear portion 21 of the grid 2 extends is the y direction, and therefore the s-polarized light (indicated by Ls in FIG. 2) has an electric field component Ey. The magnetic field component (not shown) of this s-polarized light is in the x direction (Hx).

  When such s-polarized light reaches the grid 2 of the grid polarizing element, the electric field Ey of the s-polarized light is weakened by the dielectric constant of each linear portion 21. On the other hand, the medium between the linear portions 21 is often air, but generally has a dielectric constant smaller than that of the grid 2, so that the electric field Ey in the space between the linear portions 21 is as much as in the linear portions 21. Can not be weakened.

即ち、各線状部２１間の中央の電界Ｅｙの最も高いところを境に、一方の側ではＨｚは光の伝搬方向前方に向き、他方の側ではＨｚは後方を向く。ここで、図２では省略されているが、ｘ方向の磁界ＨｘはＥｙと同位相で、ｘ軸負の側を向いて存在している。このｘ方向磁界成分Ｈｘは、生成されたｚ方向成分Ｈｚに引っ張られ、波打つように変形する。 As a result, a rotation component of the electric field Ey is generated in the xy plane. Then, according to the following Maxwell equation (Formula 1) corresponding to Faraday's electromagnetic induction, two mutually opposite magnetic fields Hz are induced in the z direction in accordance with the strength of rotation in the xy plane.

That is, on the one side, Hz is directed forward in the light propagation direction, and on the other side, Hz is directed backward, with the central electric field Ey between the linear portions 21 being the highest. Here, although omitted in FIG. 2, the magnetic field Hx in the x direction has the same phase as Ey and exists toward the negative side of the x axis. The x-direction magnetic field component Hx is pulled by the generated z-direction component Hz and deforms so as to wave.

この様子が、図３において模式的に示されており、ｘ方向磁界成分Ｈｘの波打ち（回転）により新たに電界Ｅｙが発生する様子が模式的に示されている。 When such undulation (rotation) of the magnetic field component Hx occurs, an electric field is further generated in the y direction in FIG. 2 by the Maxwell equation (Equation 2) corresponding to Ampere-Maxwell's law.

This state is schematically shown in FIG. 3, and a state in which an electric field Ey is newly generated by the wave (rotation) of the x-direction magnetic field component Hx is schematically shown.

  As shown in FIG. 3, due to the undulation (rotation) of the magnetic field component Hx in the xz plane, an electric field Ey directed toward the front side of the page of FIG. In the meantime, an electric field Ey directed toward the back side of the paper surface is generated. In this case, since the original electric field Ey of the incident s-polarized light is directed toward the front side of the page, the electric field between the linear portions 21 is canceled by the rotation of the magnetic field, and acts so that the wave is divided. As a result, the electric field Ey is localized in each linear portion 21 in the grid 2, and the energy of the s-polarized light disappears while propagating through the grid 2 due to absorption according to the material of the linear portion 21.

  On the other hand, for p-polarized light, the electric field component is oriented in the x direction (Ex), but when viewed in the y direction, the dielectric constant distribution is uniform, so the electric field rotation component as described above is substantially Does not occur. Therefore, the localization of the electric field such as s-polarized light in the grid 2 and the attenuation in each linear portion 21 do not occur in the p-polarized light. That is, the electric field Ey is localized in each linear portion 21 by causing the magnetic field component Hx to wave (rotate) with respect to the s-polarized light, and the s-polarized light is selectively attenuated by absorption in each linear portion 21. What is going on is an absorptive operation model employed in the grid polarizing element of this embodiment. Although such an absorption-type operation model can be used for polarization of light in the visible range, it can be suitably used for polarization of light in the ultraviolet range where absorption is likely to increase in the grid material.

In the case of such a grid polarizing element operating in the absorption type, it is preferable that the aspect ratio (h / w in FIG. 1) of each linear portion 21 of the grid 2 is larger. As can be seen from FIG. 2 and FIG. 3, attenuation due to absorption of the s-wave by each linear portion 21 occurs in the propagation direction of the s-wave, that is, the height direction of each linear portion 21, and the higher the aspect ratio is, the more the aspect ratio is. This is because the attenuation of the s-wave increases (that is, the extinction ratio increases). For example, in the case of the grid 2 made of titanium nitride or titanium oxynitride, the aspect ratio is preferably 3 or more, and more preferably 5 or more.
More specific dimensions will be described. For example, in the case of the application of polarizing near ultraviolet rays of 200 to 380 nm, the width w of each linear portion 21 is about 15 to 50 nm, the height is about 70 to 300 nm, and the aspect ratio is 5 to 5. It is about 15 nm. The gap width t that greatly affects the polarization performance is about 30 to 150 nm (in the case of polarizing ultraviolet light).

Next, the suitable manufacturing method of such a grid polarizing element of 1st embodiment is demonstrated. FIG. 4 is a schematic front sectional view showing a preferred method for manufacturing the grid polarizing element of the first embodiment.
As described above, the grid polarizing element is manufactured using thin film formation and photolithography techniques. The grid polarizing element of the embodiment is for ultraviolet light polarization, and in order to obtain a grid structure with a high aspect ratio, the manufacturing method shown in FIG. 4 is a method of temporarily forming a layer called a sacrificial layer. .

  More specifically, the thin film 30 is made of a material that becomes a sacrificial layer with respect to the transparent substrate 1 (FIG. 4A). Then, after performing resist coating, exposure, and development, etching using the resist pattern as a mask is performed to form a sacrificial layer 31 (FIG. 4B). The sacrificial layer 31 is also striped like the grid.

And the titanium nitride thin film 20 for grids is created so that the sacrificial layer 31 may be covered (FIG. 4 (3)). The titanium nitride thin film 20 is formed on the upper and side surfaces of each sacrificial layer 31 and the exposed surface of the transparent substrate 1.
Next, the titanium nitride thin film 20 is selectively removed by anisotropic etching. The etchant is directed by the electric field and penetrates along the height direction of each sacrificial layer 31. For this reason, the titanium nitride thin film 20 is removed on the upper surface of each sacrificial layer 31 and the exposed surface of the transparent substrate 1, and the titanium nitride thin film 20 remains only on the side surfaces of each sacrificial layer 31 (FIG. 4 (4)).

Thereafter, when etching is performed using an etchant capable of removing only the sacrificial layer 31, the grid 2 in which the respective linear portions 21 made of titanium nitride are formed on the transparent substrate 1 is obtained. A grid polarizing element is completed (FIG. 4 (5)).
The material of the sacrificial layer 31 is not particularly limited as long as it is resistant to an etchant during etching of the titanium nitride thin film 20 and can be selectively removed by etching after the formation of each linear portion 21. can do. For example, silicon is selected as the material for the sacrificial layer 31.

In the above manufacturing method, in order to obtain the grid 2 with good dimensional accuracy, it is important to form the titanium nitride thin film 20 with a sufficient and controlled film thickness on the side surface of each sacrificial layer 31. For this reason, ALD (Atomic Layer Deposition) is preferably employed as the film forming method.
Specifically, a titanium complex such as titanium tetrachloride (TiCl ₄ ) is used as the source gas, and the first precursor gas generated in the high frequency inductively coupled plasma reaches the transparent substrate 1 for adsorption. And form a monoatomic layer by saturation. And after removing excess source gas by inert gas purge, the 2nd precursor gas similarly generated in the high frequency inductively coupled plasma is made to reach on the transparent substrate 1, and a reaction is completed. This process is repeated to grow a film for each atomic layer. The number of repetitions depends on the thickness of the titanium nitride thin film 20 to be created, but is, for example, about 500 to 1500 times.
In the case of ALD, since adsorption and saturation (self-stop) on the surface are used, a film can be sufficiently formed on the inner surface of the fine structure such as the side surface of the sacrificial layer 31, and the number of repetitions can be defined and selected. There is an advantage that the film thickness can be accurately controlled. For this reason, it uses suitably in manufacture of the grid polarizing element of embodiment.

Next, the result of the simulation which investigated polarization | polarized-light performance is demonstrated about an example (Example) of the grid polarizing element of the above embodiments. FIG. 5 is a diagram showing the results of a simulation in which the polarization performance was examined for an example of a grid polarizing element.
In this simulation, when the grid 2 is made of titanium nitride, the width w of each linear portion 21 is 20 nm, the height h is 170 nm, and the gap width t is 70 nm, and the grid polarizing element is configured, the transmittance TR at each wavelength and The extinction ratio ER was calculated. For comparison, the transmittance TR and the extinction ratio ER were also obtained in the same manner when titanium oxide was used as the grid material and the dimensions were exactly the same. Optical constants are required to calculate the transmittance and extinction ratio, but the optical constants of titanium nitride and titanium oxide are published by SOPRA, France (Sopra SA, 26 Rue Pierre Joigneaux Bois-Colombes 92270 FRANCE). Values disclosed in the N & K database were used. The simulation is in accordance with the RCWA (Rigorous Coupled-Wave Analysis) method, and software distributed by the National Institute of Standards and Technology (NIST) (http://physics.nist.gov/Divisions/Div844 /facilities/scatmech/html/grating.htm).

In FIG. 5, (1) indicates the transmittance TR, and (2) indicates the extinction ratio ER. In each case, the horizontal axis is the wavelength (nm). In addition, the vertical axis | shaft of FIG. 5 (2) is a logarithmic scale. In FIG. 5 (1), TR_TiN is the transmittance in the case of a titanium nitride grid, and TR_TiO2 is the transmittance in the case of a titanium oxide grid. In FIG. 5 (2), ER_TiN is an extinction ratio in the case of a titanium nitride grid, and ER_TiO2 is an extinction ratio in the case of a titanium oxide grid.
As shown in FIG. 5 (1), in the wavelength range of 300 to 390 nm, the grid made of titanium oxide shows higher transmittance, but in the wavelength range of about 250 to 300 nm, the grid made of titanium nitride is The transmittance is almost the same as that of the grid made of titanium oxide.

Further, as shown in FIG. 5 (2), in the wavelength region of about 300 to 390 nm, the grid made of titanium nitride shows a slightly higher extinction ratio than the grid made of titanium oxide. In the range of 260 to 300 nm, on the contrary, the titanium oxide grid has a slightly higher extinction ratio, but it is reversed at 260 nm or less, and the titanium nitride grid is higher.
The extinction ratio of about 7 to 8 or more is often sufficient, and the titanium nitride grid can be used sufficiently even in the range of about 320 to 390 nm.

As described above, the simulation shows that the titanium nitride grid and the titanium oxide grid have almost the same polarization performance, although the wavelength is superior or inferior depending on the wavelength. In FIG. 5, the case of a grid made of titanium oxynitride is not shown, but it can be easily estimated that polarization performance with no great difference can be obtained.
However, the extinction ratio of the grid made of titanium nitride in the wavelength region of 260 nm or less is higher than that of the grid made of titanium oxide. Therefore, in applications that polarize light in this wavelength range, particularly applications that require polarized light with a high extinction ratio, the titanium nitride grid may have a great advantage.
In any case, these simulation results show that, according to the grid made of titanium nitride or the grid made of titanium oxynitride, there is no significant deterioration in polarization characteristics even if oxidation occurs in part, and good polarization performance is stabilized. It is shown that it can be obtained.

As described above, the titanium nitride thin film is formed by ALD using, for example, titanium tetrachloride (TiCl ₄ ) as a raw material gas. However, when more specific conditions are shown, as a plasma for activating the raw material gas, A high-frequency plasma having an input power in the discharge space of about 300 to 1000 W is used. The temperature of the transparent substrate during film formation is 200 to 600 ° C., and nitrogen is used as the purge gas. The number of stacked atomic layers (the number of repetitions) is about 500 to 1500, and the thickness of the titanium nitride thin film to be formed is about 12 to 36 nm.

Next, the grid polarizing element of 2nd embodiment is demonstrated. FIG. 6 is a schematic front sectional view of the grid polarizing element of the second embodiment.
In the grid polarizer of the second embodiment shown in FIG. 6, the main layer 21 a is formed of titanium oxynitride in each linear portion 21 that forms the grid 2. As shown in FIG. 6, each linear portion 21 has a layer 21b that follows the inside, and this layer 21b is formed of titanium oxide. As shown in FIG. 6, the subordinate layer 21 b made of titanium oxide is less than 50% with respect to the cross-sectional area of the entire linear portion 21, and thus has a volume of less than 50%.

FIG. 7 is a schematic front sectional view showing a method for manufacturing the grid polarizer of the second embodiment shown in FIG.
When manufacturing the grid polarizing element of 2nd embodiment, the thin film 30 is similarly produced with the material used as a sacrificial layer with respect to the transparent substrate 1 (FIG. 7 (1)). Then, resist application, exposure, and development are performed, and etching using the resist pattern as a mask is performed to form a sacrificial layer 31 (FIG. 7B).

And the titanium oxide thin film 40 for grids is created so that the sacrificial layer 31 may be covered (FIG. 7 (3)). The titanium oxide thin film 40 is formed on the upper and side surfaces of each sacrificial layer 31 and the exposed surface of the transparent substrate 1.
Next, the titanium oxide thin film 40 is selectively removed by anisotropic etching. Similarly, the etchant is directed by an electric field, the titanium oxide thin film 40 is removed on the upper surface of each sacrificial layer 31 and the exposed surface of the transparent substrate 1, and the titanium oxide thin film 40 is left only on the side surface of each sacrificial layer 31 (FIG. 7 (4)).

Thereafter, etching is similarly performed using an etchant that can remove only the sacrificial layer 31, so that the linear portions 41 made of titanium oxide are formed on the transparent substrate 1 (FIG. 7 (5)).
After that, each linear portion 41 is subjected to nitriding treatment so that each linear portion 21 is formed of a main layer 21a made of titanium oxynitride and a subordinate layer 21b made of titanium oxide. For example, a method is adopted in which each linear portion 41 is exposed to nitrogen plasma and subjected to nitriding treatment by the action of nitrogen ions or nitrogen active species in the plasma. Nitriding occurs from the surface of each linear portion 41, but each linear portion 41 is a nano-sized fine one, and can be nitrided to the inside of each linear portion 41 by being exposed to nitrogen plasma for a certain period of time. In other words, the layer 21a made of titanium oxynitride can be formed in a cross-sectional area of 50% or more. Thereafter, the grid polarization element is finally completed through the cleaning process and the like (FIG. 7 (6)).

  Also in the grid polarizing element of the second embodiment, each linear portion 21 forming the grid 2 has a layer made of chemically stable titanium oxynitride as a main layer 21a having appropriate light absorption characteristics. A grid polarizing element that operates in an absorption model can be obtained, and even if it is used in an environment that easily oxidizes, deterioration of polarization characteristics does not become a problem. For this reason, it becomes a grid polarization element especially suitable when polarizing with ultraviolet rays as a target wavelength.

Moreover, since the grid 21 made of titanium oxynitride is obtained by nitriding after forming each linear portion 41 with titanium oxide, the manufacturing process is simple and etching a multilayer film of different materials including a single metal layer. There is no difficulty to do. Note that the entire inside of the linear portion 41 may be nitrided, and in this case, each linear portion 21 is formed only by the main layer 21a made of titanium oxynitride.
In the above manufacturing method, ALD can also be suitably employed for the production of the titanium oxide thin film 40, and titanium tetrachloride (TiCl ₄ ) or the like can be used as a source gas. Further, as in the case of titanium nitride, various fine processing techniques established in the semiconductor process can be applied to titanium oxide.

  In the second embodiment, the titanium oxide thin film 40 is prepared as a thin film for a grid, and the main layer 21a made of titanium oxynitride is formed by nitriding this. However, the titanium nitride thin film is formed as a thin film for a grid. A main layer made of titanium oxynitride may be formed by forming a thin film and oxidizing it. For the oxidation treatment, for example, oxygen plasma treatment performed by exposure to oxygen plasma formed by high-frequency discharge can be employed. In this case, the oxidation treatment is performed only on the surface region of titanium nitride, and other regions may be left as titanium nitride.

Next, another embodiment of the grid polarizing element will be described. FIG. 8 is a schematic front sectional view of another embodiment of a grid polarizing element.
The grid polarizing element of the present invention can be implemented in various forms other than the first and second embodiments described above. For example, as shown in FIG. 8A, each linear portion 21 is formed of two upper and lower layers, one of which is a first layer 211 made of titanium nitride, and the other is a second layer made of titanium oxynitride. 212. In this case, the first layer 211 and the second layer 212 may be reversed.

Further, as shown in FIG. 8B, a first layer 213 made of titanium nitride and a second layer 214 made of titanium oxynitride are provided side by side in contact with each other. A structure in which one linear portion 21 is formed may be employed.
Further, as shown in FIG. 8C, second layers 216, 217 made of titanium oxynitride are provided on both sides of the first layer 215 made of titanium nitride, and the layers 215, 216, 217 are in contact with each other. The structure may be a state. Also in this case, the relationship between the first layer 215 and the second layers 216 and 217 may be reversed.
Each of the embodiments shown in FIG. 8 is an embodiment in which a main layer is formed of a titanium nitride layer and a titanium oxynitride layer. That is, the main layer may be formed of only titanium nitride, may be formed of only titanium oxynitride, or may be formed of both.

Next, embodiments of the invention of the ultraviolet polarized light irradiation method and the invention of the ultraviolet polarized light irradiation apparatus will be described. The following description relates to a photo-alignment apparatus and a method for manufacturing a substrate with a photo-alignment layer, but is a method and apparatus using a mercury lamp, and the implementation of each invention of an ultraviolet-polarized light irradiation method and an ultraviolet-polarized light irradiation apparatus. It also serves as an explanation of the form.
FIG. 9 is a diagram illustrating an outline of the method for manufacturing the substrate with a photo-alignment layer according to the embodiment, and is a schematic cross-sectional view of the photo-alignment apparatus. The photo-alignment device shown in FIG. 9 is a photo-alignment device for obtaining a photo-alignment layer in the production of a liquid crystal display or the like. By irradiating the film for the photo-alignment layer with polarized light, the molecular structure of the film is constant. It is in a state of being aligned in the direction. Therefore, the workpiece 10 is a substrate such as a liquid crystal substrate on which a film for a photo-alignment layer is formed. The film for the photo-alignment layer is made of polyimide, for example.

  The optical alignment apparatus shown in FIG. 9 linearly moves the stage 6 so as to pass through the irradiation region, the light irradiator 5 that irradiates the set irradiation region with polarized light, the stage 6 on which the work 10 is placed, and the irradiation region. And a transport mechanism 7 that allows the workpiece 10 on the stage 6 to pass through the irradiation region. Although details of the transport mechanism 7 are omitted in FIG. 9, a linear movement mechanism combining a ball screw and a linear guide is usually employed. In addition, the film of the photo-alignment layer itself may be a workpiece. In this case, for example, a transport mechanism that transports a sheet-like film made of polyimide by roll-to-roll is adopted, and polarized light is irradiated during the transport. Is done.

The light irradiator 5 includes a light source 51, a mirror 52 covering the back of the light source 51, and a grid polarizing element 53 disposed between the light source 51 and the workpiece 10. The grid polarization element 53 is that of the above-described embodiment.
Since light irradiation requires ultraviolet irradiation, a long arc type low-pressure mercury lamp or high-pressure mercury lamp is used as the light source 51. In general, a low-pressure mercury lamp with a sealed pressure of 100 Pa or less is used, and a high-pressure mercury lamp is used with the pressure inside it. The light source 51 is long in the direction perpendicular to the conveyance direction of the workpiece 10 (here, the direction perpendicular to the paper surface). The mirror 52 is a long pair extending in the same direction as the light source 51, and the cross-sectional shape of the reflecting surface is a parabolic shape or an elliptical arc shape.

As described above, the grid polarization element 53 selectively transmits p-polarized light based on the grid length. Therefore, the grid polarization element 53 is arranged with high posture accuracy with respect to the workpiece 10 so that the polarization axis of the p-polarized light is directed in the direction of performing the optical alignment.
In addition, since it is difficult to manufacture a large-sized grid polarizing element 53, when it is necessary to irradiate polarized light to a large area, a configuration in which a plurality of grid polarizing elements 53 are arranged on the same plane is adopted. . In this case, the surface on which the plurality of grid polarizing elements 53 are arranged is parallel to the surface of the workpiece 10, and each grid is arranged such that the length direction of the grating in each grid polarizing element 53 is a predetermined direction with respect to the workpiece 10. A polarizing element 53 is disposed.

  In the irradiation region, the work 10 is irradiated with polarized light through the grid polarizing element 53. As a result, the molecular structure of the film for the photo-alignment layer formed on the workpiece 10 is aligned with the direction of the polarization axis of the polarized light, and a photo-alignment layer is obtained. That is, a substrate with a photo-alignment layer is manufactured. When the work is a film material for photo-alignment conveyed by roll-to-roll, after the photo-alignment process, it is cut into an appropriate size and attached to the substrate. Thereby, the board | substrate with a photo-alignment layer is manufactured.

  As described above, the grid polarizing element 53 in which each linear portion of the grid is formed of titanium nitride has a polarization characteristic that increases the extinction ratio in a wavelength region of 260 nm or less. A high extinction ratio means that the purity of the polarized light (purity with respect to the direction of the polarization axis) is high, and that the photo-alignment is performed more clearly. On the other hand, as is well known, the low-pressure mercury lamp has a strong emission line spectrum at 254 nm and 185 nm. Therefore, the photo-alignment apparatus combining such a mercury lamp and the grid polarizing element 53 of the grid made of titanium nitride brings an excellent result that a photo-alignment layer with higher quality can be obtained with high productivity.

Even when the material of the grid is titanium oxynitride, it is estimated that a high extinction ratio is exhibited with respect to the emission line spectrum of 254 nm if not as much as titanium nitride, and it is considered that almost the same effect can be obtained. Such an effect is particularly significant in the application of photo-alignment, but it is generally appropriate not only for photo-alignment but also for applications that require irradiation of high-quality polarized light with high quality at wavelengths in the ultraviolet region.
In the above description, the optical alignment apparatus is provided with the transport mechanism 7. However, it is also possible to simply provide means (for example, the stage 6) for placing the work 10 in the polarized light irradiation region. .

In the grid polarizing element of each of the embodiments described above, the films 20 and 40 that form the main layer of each linear portion 21 are formed by ALD, but may be formed by other methods such as CVD or sputtering.
Further, in the above description, the target wavelength is exclusively focused on the polarization of ultraviolet rays in the ultraviolet region, particularly in the wavelength region of 260 nm or less, but the grid polarization of each embodiment is also used for polarization of ultraviolet rays in the wavelength region of 260 to 380 nm (eg 365 nm) The element can be suitably used.
In the grid polarization element, the gap is described as air between the linear portions 21 of the grid 2, but an appropriate material may be filled in the gap.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Grid 21 Linear part 21a Main layer 21b Subordinate layer 31 Sacrificial layer 5 Light irradiator 51 Light source 6 Stage 7 Transport mechanism

Claims (9)

A grid that consists of a transparent substrate and a striped grid formed of a large number of linear parts provided on the transparent substrate, and selectively polarizes light by selectively transmitting specific polarized light from incident light. A polarizing element,
The non-reflective grid polarizing element characterized in that a large number of linear portions forming the grid have a main layer formed of titanium nitride or titanium oxynitride and do not include a single metal layer.   2. The non-reflective grid polarizing element according to claim 1, wherein h / w is 3 or more, where w is a width and h is a height of each linear part forming the grid.   The linear portion is a process in which light propagates in the thickness direction of the linear portion, and compared to polarized light whose polarization axis is oriented in a direction perpendicular to the length direction of each linear portion, The grid polarizing element according to claim 1 or 2, wherein the polarized light is polarized by absorbing a large amount of polarized light having a polarization axis in the length direction.   The non-reflective grid polarizing element according to claim 1, 2 or 3, wherein the spacing between the linear portions forming the grid is a spacing capable of polarizing ultraviolet rays.   The non-reflective grid polarizing element according to claim 4, wherein the spacing between the linear portions forming the grid is 100 nm or more and 200 nm or less.   The non-reflective grid polarizing element according to claim 4 or 5 is disposed at a position where light from a mercury lamp including an emission line spectrum of 260 nm or less reaches, and polarized light transmitted through the non-reflective grid polarizing element is an object. Irradiating with ultraviolet polarized light. A mercury lamp that emits light having an emission line spectrum of 260 nm or less;
An ultraviolet polarized light irradiation apparatus comprising: the non-reflective grid polarizing element according to claim 4 or 5 disposed at a position where light from the mercury lamp reaches.   The non-reflective grid polarizing element according to claim 4 or 5 is disposed at a position where light reaches from a light source that emits ultraviolet light, and the ultraviolet polarized light transmitted through the non-reflective grid polarizing element is used as a film for a photo-alignment layer. The manufacturing method of the board | substrate with a photo-alignment layer characterized by including the process of irradiating to. An ultraviolet light source,
The non-reflective grid polarizing element according to claim 4 or 5 disposed at a position where light from an ultraviolet light source reaches,
A photo-alignment device comprising: means for transporting or arranging a film for a photo-alignment layer at a position where polarized light transmitted through the non-reflective grid polarization element is irradiated.

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